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Article by Ed Baker, Planner (Tree Officer), City of Cardiff Council
The soil is a dark, mysterious world. Until we put a spade into it or look at it under a microscope, we can fail to appreciate its complexity and the kaleidoscope of life it supports. It then becomes ‘muck’ or ‘dirt’, to be shifted, sifted and squashed to support development. So long as we tear it up with a big metal claw and add a bit of muck to it, it will grow us big trees without complaint, won’t it?
Often we are told that trees have died because they have had too little or too much water, when the real problem is soil that has been turned into a lifeless, concrete porridge, into which a pampered nursery tree has been dropped and then, to ‘help it out’, surrounded by a quagmire of compost and fertiliser!
For those of us professionally involved in the care and cultivation of amenity trees, failure to get things right from the bottom up is failure full stop. Arboriculture is no different from agriculture in that it begins and ends with the soil.
Many of our towns and cities are developing fast, and soils untouched by ought but a plough since the end of the last ice age face potentially catastrophic damage. Yet with careful assessment and handling, the best of these soils can be protected so that they support the growth of large trees, giving back to the soil what centuries of farming and more recent development have taken out.
To ensure that the best soils are protected and re-used appropriately, they should be professionally assessed by a soil scientist in accordance with the 2009 Defra ‘Construction Code of Practice for the Sustainable Use of Soils on Construction Sites’. This results in a Soil Resource Survey (SRS) and Soil Resource Plan (SRP) that should inform landscaping specifications and construction environmental management plans. In the same way that an arboriculturist should oversee tree protection on a development site, a soil scientist should oversee soil handling, storage, amelioration and placement, in accordance with the SRP.
Leaving soil handling to groundworks or geotechnical contractors alone may result in a development that satisfies engineering requirements of the soil, but may be less suitable for supporting the establishment and healthy growth of vegetation, particularly large trees. The consequence could be costly in environmental and financial terms, requiring extensive soil amelioration, soil importation and replacement of planting failures.
Relying on generic soil specifications and compliance with British Standards may result in the widespread use of imported, ‘as dug’ or manufactured, ‘multi-purpose’ soils, even when existing in situ or site-won soils could be equally or more effective at supporting the proposed planting.
Different vegetation types such as wildflower grassland, amenity grassland and large, root-balled trees have differing ‘performance’ requirements of the soil, and generic specifications, or those that meet the relatively broad criteria of the British Standards only, may result in poor performance or failures.
Over-specification of topsoil and underspecification of subsoil are common problems with regard to tree planting, with some considering that large trees require a deep hole full of topsoil, compost and fertiliser to grow successfully. The result of this can be oxygen depletion, excessive settlement, spiralling roots and ‘sump’ conditions, so that planting holes become bogs, with the smells to go with it! Anybody who has dug trenches to expose a soil profile knows that in nature ‘topsoil’ depths typically extend no deeper than 400mm, often much less, yet it is still common to see tree pit sections showing topsoil enveloping root-balls to 600mm depth, ‘enriched’ with composts and fertiliser and surrounded by soil of unknown specification.
Subsoil on the other hand is often ignored, or simply proposed for ‘ripping’, without evidence from a soil scientist that this will be necessary or effective, or a description of the methods and equipment to be used. Particularly where larger trees are being planted, subsoil with optimal qualities of aeration and drainage, including under the loading of a large root-ball, is essential to effective establishment. Ensuring that provision is made in practical and financial terms for effective subsoil handling, amelioration or importation is essential, wherever large tree planting is proposed.
Cardiff Council is preparing guidance on soils and development, but this does not seem to be a widespread approach. It will be a learning process, no doubt subject to refinement over time, but the more local authorities develop this sort of guidance, and share knowledge on best practice and local success stories, the better it will be, not only for soils, but in turn for trees and people.
Should you wish to discuss the draft soils and development guidance that is in preparation, please contact treeprotection@cardiff.gov.uk.

Article by Ed Baker, Planner (Tree Officer), City of Cardiff Council
The soil is a dark, mysterious world. Until we put a spade into it or look at it under a microscope, we can fail to appreciate its complexity and the kaleidoscope of life it supports. It then becomes ‘muck’ or ‘dirt’, to be shifted, sifted and squashed to support development. So long as we tear it up with a big metal claw and add a bit of muck to it, it will grow us big trees without complaint, won’t it?
Often we are told that trees have died because they have had too little or too much water, when the real problem is soil that has been turned into a lifeless, concrete porridge, into which a pampered nursery tree has been dropped and then, to ‘help it out’, surrounded by a quagmire of compost and fertiliser!
For those of us professionally involved in the care and cultivation of amenity trees, failure to get things right from the bottom up is failure full stop. Arboriculture is no different from agriculture in that it begins and ends with the soil.
Many of our towns and cities are developing fast, and soils untouched by ought but a plough since the end of the last ice age face potentially catastrophic damage. Yet with careful assessment and handling, the best of these soils can be protected so that they support the growth of large trees, giving back to the soil what centuries of farming and more recent development have taken out.
To ensure that the best soils are protected and re-used appropriately, they should be professionally assessed by a soil scientist in accordance with the 2009 Defra ‘Construction Code of Practice for the Sustainable Use of Soils on Construction Sites’. This results in a Soil Resource Survey (SRS) and Soil Resource Plan (SRP) that should inform landscaping specifications and construction environmental management plans. In the same way that an arboriculturist should oversee tree protection on a development site, a soil scientist should oversee soil handling, storage, amelioration and placement, in accordance with the SRP.
Leaving soil handling to groundworks or geotechnical contractors alone may result in a development that satisfies engineering requirements of the soil, but may be less suitable for supporting the establishment and healthy growth of vegetation, particularly large trees. The consequence could be costly in environmental and financial terms, requiring extensive soil amelioration, soil importation and replacement of planting failures.
Relying on generic soil specifications and compliance with British Standards may result in the widespread use of imported, ‘as dug’ or manufactured, ‘multi-purpose’ soils, even when existing in situ or site-won soils could be equally or more effective at supporting the proposed planting.
Different vegetation types such as wildflower grassland, amenity grassland and large, root-balled trees have differing ‘performance’ requirements of the soil, and generic specifications, or those that meet the relatively broad criteria of the British Standards only, may result in poor performance or failures.
Over-specification of topsoil and underspecification of subsoil are common problems with regard to tree planting, with some considering that large trees require a deep hole full of topsoil, compost and fertiliser to grow successfully. The result of this can be oxygen depletion, excessive settlement, spiralling roots and ‘sump’ conditions, so that planting holes become bogs, with the smells to go with it! Anybody who has dug trenches to expose a soil profile knows that in nature ‘topsoil’ depths typically extend no deeper than 400mm, often much less, yet it is still common to see tree pit sections showing topsoil enveloping root-balls to 600mm depth, ‘enriched’ with composts and fertiliser and surrounded by soil of unknown specification.
Subsoil on the other hand is often ignored, or simply proposed for ‘ripping’, without evidence from a soil scientist that this will be necessary or effective, or a description of the methods and equipment to be used. Particularly where larger trees are being planted, subsoil with optimal qualities of aeration and drainage, including under the loading of a large root-ball, is essential to effective establishment. Ensuring that provision is made in practical and financial terms for effective subsoil handling, amelioration or importation is essential, wherever large tree planting is proposed.
Cardiff Council is preparing guidance on soils and development, but this does not seem to be a widespread approach. It will be a learning process, no doubt subject to refinement over time, but the more local authorities develop this sort of guidance, and share knowledge on best practice and local success stories, the better it will be, not only for soils, but in turn for trees and people.
Should you wish to discuss the draft soils and development guidance that is in preparation, please contact treeprotection@cardiff.gov.uk.
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By Simon Richmond
The tragic deaths of arborists have recently been in our minds. Paul Kirkley’s article brings everything into sharp definition and we owe it to him, to the memory of Alex and Greg, and of course to all arborists, to take this opportunity to scrutinise possible causes of these accidents and of course to do all we can to prevent any more.
In response to the coroner’s ‘Prevention of Future Deaths’ report and request for a response from the Arboricultural Association, we met with the Health and Safety Executive (HSE) and chainsaw manufacturers to consider the overall issues. Paul Kirkley’s analysis of how his son’s accident occurred and the causal factors around the issue of kickback in top-handled saws led us to realise that, while we may have our own opinions and assumptions about what our members and others in the industry may think, we had no evidence of this.
So, we issued a Health and Safety Survey which was widely distributed to all AA members and many others who are not currently members.
We were overwhelmed by the response to this – over 500 people replied.
We asked about perceptions of safe working practice, hazards and risk, and the potential root causes of chainsaw injuries; we also asked whether physical, mechanical guarding of the chainsaw tip was seen as a useful control.
The largest group of respondents were practising arborists who use top-handled chainsaws daily. When asked about the different types of accident that were most likely, the answers were well spread across the range; however, when asked what the root cause of such accidents would be, less than 5% thought kick back would be responsible, with nearly 24% citing one-handed chainsaw use and nearly 60% identifying poor work positioning.
‘Time pressures’ and ‘fatigue/loss of concentration’ were considered to be the most likely contributory factors with ‘industry/workplace culture (bravado)’ following close behind. 72% of respondents felt that the current training and certification options for climbing arborists were adequate (28% did not). Most said that they did not experience kickback regularly.
There were over 300 written comments (which space does not allow me to reproduce here) to offer opinions about our industry culture, training, causal issues and improvements to chainsaw design and/or use.
When asked about technological improvements to top-handled chainsaws, the most common proposals were:
improved bar/chain combinations (carving bars/safety chain)
safety sensor/control to prevent onehanded operation
However, a large proportion of comments suggested that ‘it is not the saw that is the problem – they’re already well designed’.
Just over half of the respondents had heard about chainsaw bar ‘tip guards’ and around 65% felt that their use would compromise working practice when using the saw for compound cuts (e.g. when section felling).
Finally, we asked ‘Would you feel safer knowing that the saw could not kick back?’ 55% answered ‘No’.
The results of the survey were presented to Paul Kirkley at AA’s offi ces on 3 April, and he agreed to write an article for the magazine, as published on the previous pages.
We also sent the results to the HSE and these were presented to the HSE’s Arboriculture and Forestry Advisory Group (AFAG) committee on 16 May.
The issues raised by these accidents were discussed by the broad range of expertise that is represented on the AFAG committee. There was universal appreciation of the extensive research that Mr Kirkley had contributed and each of his recommendations was considered. After a comprehensive discussion, it was agreed that the proposal for fi tting bar tip guards to top-handled saws was unlikely to be a practical solution. The suggestion, from his response to HSE, that some form of PPE for the operator’s neck area could be made available was also discussed at length. The committee doubted the practicality of this, either of it technically being able to perform to normal chainsaw protection standards, or being a sustainable solution from an operator comfort perspective. However, STIHL has offered the services of its technical research team in Germany to carry out a desk-based review, to investigate if such a PPE garment is feasible.
All agreed that we need to improve the provision of emergency planning and first aid for all aerial operations. While this would not have saved Alexander Kirkley’s life, as his injury was so traumatic, there are many circumstances where a properly planned and effi ciently executed rescue and fi rst aid provision will make the difference between life and death.
The conclusions of the group were that the technical advancement of saws for use in the tree has progressed rapidly over the last few years and no doubt will continue to do so; the use of better bar/chain combinations to reduce kick back should be encouraged. However, it was generally agreed that the most important contribution to improved safe working was around behavioural and management issues, including better consolidation of experience under supervision and improved work planning, taking time to secure the correct, safe work position for every cut using both hands on the saw, and maintaining communication with others on site. Contrary to some rumours, there was comprehensive agreement that the top-handled chainsaw is an essential tool for aerial tree work and there is no proposal to restrict or ban its use.
The chair of AFAG is now due to write to Mr Kirkley to inform him of the committtee’s conclusions, and to the coroner who had raised the ‘Prevention of Future Deaths’ report.

By Simon Richmond
The tragic deaths of arborists have recently been in our minds. Paul Kirkley’s article brings everything into sharp definition and we owe it to him, to the memory of Alex and Greg, and of course to all arborists, to take this opportunity to scrutinise possible causes of these accidents and of course to do all we can to prevent any more.
In response to the coroner’s ‘Prevention of Future Deaths’ report and request for a response from the Arboricultural Association, we met with the Health and Safety Executive (HSE) and chainsaw manufacturers to consider the overall issues. Paul Kirkley’s analysis of how his son’s accident occurred and the causal factors around the issue of kickback in top-handled saws led us to realise that, while we may have our own opinions and assumptions about what our members and others in the industry may think, we had no evidence of this.
So, we issued a Health and Safety Survey which was widely distributed to all AA members and many others who are not currently members.
We were overwhelmed by the response to this – over 500 people replied.
We asked about perceptions of safe working practice, hazards and risk, and the potential root causes of chainsaw injuries; we also asked whether physical, mechanical guarding of the chainsaw tip was seen as a useful control.
The largest group of respondents were practising arborists who use top-handled chainsaws daily. When asked about the different types of accident that were most likely, the answers were well spread across the range; however, when asked what the root cause of such accidents would be, less than 5% thought kick back would be responsible, with nearly 24% citing one-handed chainsaw use and nearly 60% identifying poor work positioning.
‘Time pressures’ and ‘fatigue/loss of concentration’ were considered to be the most likely contributory factors with ‘industry/workplace culture (bravado)’ following close behind. 72% of respondents felt that the current training and certification options for climbing arborists were adequate (28% did not). Most said that they did not experience kickback regularly.
There were over 300 written comments (which space does not allow me to reproduce here) to offer opinions about our industry culture, training, causal issues and improvements to chainsaw design and/or use.
When asked about technological improvements to top-handled chainsaws, the most common proposals were:
improved bar/chain combinations (carving bars/safety chain)
safety sensor/control to prevent onehanded operation
However, a large proportion of comments suggested that ‘it is not the saw that is the problem – they’re already well designed’.
Just over half of the respondents had heard about chainsaw bar ‘tip guards’ and around 65% felt that their use would compromise working practice when using the saw for compound cuts (e.g. when section felling).
Finally, we asked ‘Would you feel safer knowing that the saw could not kick back?’ 55% answered ‘No’.
The results of the survey were presented to Paul Kirkley at AA’s offi ces on 3 April, and he agreed to write an article for the magazine, as published on the previous pages.
We also sent the results to the HSE and these were presented to the HSE’s Arboriculture and Forestry Advisory Group (AFAG) committee on 16 May.
The issues raised by these accidents were discussed by the broad range of expertise that is represented on the AFAG committee. There was universal appreciation of the extensive research that Mr Kirkley had contributed and each of his recommendations was considered. After a comprehensive discussion, it was agreed that the proposal for fi tting bar tip guards to top-handled saws was unlikely to be a practical solution. The suggestion, from his response to HSE, that some form of PPE for the operator’s neck area could be made available was also discussed at length. The committee doubted the practicality of this, either of it technically being able to perform to normal chainsaw protection standards, or being a sustainable solution from an operator comfort perspective. However, STIHL has offered the services of its technical research team in Germany to carry out a desk-based review, to investigate if such a PPE garment is feasible.
All agreed that we need to improve the provision of emergency planning and first aid for all aerial operations. While this would not have saved Alexander Kirkley’s life, as his injury was so traumatic, there are many circumstances where a properly planned and effi ciently executed rescue and fi rst aid provision will make the difference between life and death.
The conclusions of the group were that the technical advancement of saws for use in the tree has progressed rapidly over the last few years and no doubt will continue to do so; the use of better bar/chain combinations to reduce kick back should be encouraged. However, it was generally agreed that the most important contribution to improved safe working was around behavioural and management issues, including better consolidation of experience under supervision and improved work planning, taking time to secure the correct, safe work position for every cut using both hands on the saw, and maintaining communication with others on site. Contrary to some rumours, there was comprehensive agreement that the top-handled chainsaw is an essential tool for aerial tree work and there is no proposal to restrict or ban its use.
The chair of AFAG is now due to write to Mr Kirkley to inform him of the committtee’s conclusions, and to the coroner who had raised the ‘Prevention of Future Deaths’ report.
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